Ah in that case i didn't know there were uprated variants made in the pressed steel casing, i wouldn't be surprised if yours is standard as obviously we know the turbo is. It won't cost you anything to take the elbow off and have a look at the wastegate, thats what i would advise you do before forking any cash out.

A buzzing noise??? The only thing that springs to mind is the turbine making contact with the housing internally......but thats a shot in the dark.